1. Field
The present general inventive concept relates to a robot and a method of controlling walking thereof, and more particularly to a biped robot, which generates a stable walking pattern maximally similar to a stable walking pattern of a human, and a method of controlling walking of the robot.
2. Description of the Related Art
In general, machines, which conduct motion similar to that of a human using an electric or magnetic action, are referred to as robots. Initial robots were industrial robots, such as manipulators or transfer robots for the purpose of work automation and unmanned operation in production sites. Recently, a biped walking robot (hereinafter, referred to as a biped robot), which has a joint system similar to that of a human and easily walks with two feet in human work and living spaces, has been researched and developed.
Most biped robots have a walking pattern, in which the robot walks with knees bent and a waist moving only on a plane being parallel with the ground. In case that the knees are stretched to an angle close to 180°, a singularity pose where a relative distance connecting an ankle joint and a hip joint is equal to the length of a leg is generated, and thus a knee joint speed is excessively increased or a desired knee joint angle cannot be obtained. Further, the constraint condition of a zero moment point (hereinafter, referred to as ZMP) to obtain the walking pattern is that the center of gravity (hereinafter, referred to as COG) of a robot moves parallel with the ground. See S. Kajita et al., “Biped Walking Pattern Generation by using Preview Control of Zero-Moment Point”, ICRA2003, pp. 1620-1626.
However, such a walking pattern, in which a waist moves from side to side while maintaining a regular height on a condition that knees are considerably bent, considerably differs from that of a human.
In order to overcome the above robot walking pattern and achieve human-like walking, Waseda University has introduced a method, in which the knees are stretched and the ankles are rotated differently from the typical humanoid walking pattern. See Y. Ogura et al., “Human-like Walking with Knee Stretched, Heel-contact and Toe-off Motion by a Humanoid Robot”, IROS06, pp. 3976-3981. This method does not consider separate control for similarity to human-like walking but aims to stretch a knee angle intuitively, and thus differs from the walking pattern of a human still due to an improper point of time to stretch knees and the shaking of a waist. When a robot walks differently from the walking pattern of a human, the robot has a low affinity for a human being and a low energy efficiency. Thus, an obstacle to the spread of the biped robot in a robot and human coexistence environment exists.